<form method="POST">
    <h3>Editing: CheckoutOrderSummaryBlock.php</h3>
    <textarea name="content" rows="20" cols="80">&lt;?php
namespace Automattic\WooCommerce\Blocks\BlockTypes;

/**
 * CheckoutOrderSummaryBlock class.
 */
class CheckoutOrderSummaryBlock extends AbstractInnerBlock {
	/**
	 * Block name.
	 *
	 * @var string
	 */
	protected $block_name = 'checkout-order-summary-block';

	/**
	 * Get the contents of the given inner block.
	 *
	 * @param string $block_name Name of the order summary inner block.
	 * @param string $content    The content to search.
	 * @return array|bool
	 */
	private function get_inner_block_content( $block_name, $content ) {
		if ( preg_match( $this-&gt;inner_block_regex( $block_name ), $content, $matches ) ) {
			return $matches[0];
		}
		return false;
	}

	/**
	 * Get the regex that will return an inner block.
	 *
	 * @param string $block_name Name of the order summary inner block.
	 * @return string Regex pattern.
	 */
	private function inner_block_regex( $block_name ) {
		return '/&lt;div data-block-name=&quot;woocommerce\/checkout-order-summary-' . $block_name . '-block&quot;(.+?)&gt;(.*?)&lt;\/div&gt;/si';
	}

	/**
	 * Render the Checkout Order Summary block.
	 *
	 * @param array  $attributes Block attributes.
	 * @param string $content    Block content.
	 * @param object $block      Block object.
	 * @return string Rendered block.
	 */
	protected function render( $attributes, $content, $block ) {
		// The order-summary-totals block was introduced as a new parent block for the totals
		// (subtotal, discount, fees, shipping and taxes) blocks.
		$regex_for_checkout_order_summary_totals = '/&lt;div data-block-name=&quot;woocommerce\/checkout-order-summary-totals-block&quot;(.+?)&gt;/';
		$order_summary_totals_content            = '&lt;div data-block-name=&quot;woocommerce/checkout-order-summary-totals-block&quot; class=&quot;wp-block-woocommerce-checkout-order-summary-totals-block&quot;&gt;';

		// We want to move these blocks inside a parent 'totals' block.
		$totals_inner_blocks = array( 'subtotal', 'discount', 'fee', 'shipping', 'taxes' );

		if ( preg_match( $regex_for_checkout_order_summary_totals, $content ) ) {
			return $content;
		}

		foreach ( $totals_inner_blocks as $key =&gt; $block_name ) {
			$inner_block_content = $this-&gt;get_inner_block_content( $block_name, $content );

			if ( $inner_block_content ) {
				$order_summary_totals_content .= &quot;\n&quot; . $inner_block_content;

				// The last block is replaced with the totals block.
				if ( count( $totals_inner_blocks ) - 1 === $key ) {
					$order_summary_totals_content .= '&lt;/div&gt;';
					$content                       = preg_replace( $this-&gt;inner_block_regex( $block_name ), $order_summary_totals_content, $content );
				} else {
					// Otherwise, remove the block.
					$content = preg_replace( $this-&gt;inner_block_regex( $block_name ), '', $content );
				}
			}
		}

		// Remove empty lines.
		return preg_replace( '/\n\n( *?)/i', '', $content );
	}
}
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